modelling gas injection,help
 

hi i am modelling a gas injection system to bring up heavy oil that has not enough pressure to rise up in 2 sets of tubing size.The inner tube is for oil flow upward and outer tube is to pump the CO2 downwards and enter the inner tube at 0.25 above the oil inlet opennings while blocked by packer at the outer tube.The length of the tubes is 2.0.Is there any source of example model of gas injection like this? what is the downward underground distance should i assume to locate this system?